Now to the surveillance images coming from chicago. Those men dressed as businessmen, racing to the top for a daring stunt. And tonight police are not happy. Here's abc's alex perez. Reporter: Exhillerating, death defying, and in most cases, illegal. The jaw-dropping practice of jumping from sky-high buildings, bridges, and other big structures, known as base jumping, has a cult following that seems to be growing bolder. Police in chicago are still looking for three men who broke into the trump tower early thursday morning. It's the city's second tallest skyscra skyscraper. Made their way to the rooftop, cutting several locks to get to the 92nd story, then donned flight suits and jumped. We're looking to tomorrow what happened, who did it, and where appropriate, we'll make arrests. Reporter: It's happened in chicago before, in 2011 shawn walters took a dive from the 25th floor of this building, unknowingly landing right next to a police officer, who quickly arrested him. Professional base jumper luke achins has base jumped more than 500 times. His red bull air force team filmed this seen from the chicago trump tower per the transformers 3 movie. When you leap off, your adrenaline's pumping, it's crazy, you're like, oh my goodness. Reporter: Achins believes it's that drive for adrenaline that motivates some jumpers to break into buildings and jump, often times without the safety check list that professional jumpers would have. Alex perez, abc news, chicago.

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